Metazoan histone 3'-UTR mRNAs, lacking a polyA tail,
contain a highly conserved stem-loop structure with a
six base stem and a four base loop (HSL3). This stem-loop
structure plays a different role in the nucleus and in
the cytoplasm. In the nucleus, it is involved in pre-mRNA
processing and nucleocytoplasmic transport, whereas in the
cytoplasm it enhances translation efficiency and regulates
histone mRNA stability. The trans-acting factor which
interacts with the 3'-UTR hai......